After Wednesday's question time, Cameron was scheduled to visit Queen Elizabeth at Buckingham Palace to tender his resignation. The Queen will then receive May and call on her to form a new government.

"It's a day of some procession," Al Jazeera's Laurence Lee, reporting from London, said.

"Theresa May has to formally shake hands with the Queen, as a technical process, to then become prime minister," Lee said.

Following her audience with the Queen, there will be a photo call at Downing Street before May and her husband enter No 10 where, as new prime minister, she will announce her ministerial team, Lee said.

May's first challenge: EU departure

May, 59, is only the second woman to become prime minister in the UK..

She follows in the path of Margaret Thatcher, who held the post from 1979-90.

May's appointment as leader of the Conservative Party and prime minister is the culmination of weeks of political turmoil, party infighting and resignations following the UK’s vote to leave the European Union.

May is seen as tough on migrants, relatively hostile to EU rules on free movement of workers, and somewhat "indifferent" to the rights of EU nationals to work and reside in the UK, Lee said.

She is also "no fan" of the European Court of Human Rights, which she had previously tussled with her as home secretary, he added.

While she might be characterised as "socially illiberal", Lee said, May set out on Monday an economic programme as prime minister-in-waiting that was particularly left-leaning.

May's first challenge as prime minister will be to map out the course of Britain's withdrawal from the EU, a process still clouded in uncertainty, and to sort out new terms of trade with the other 27 EU nations.

European leaders have asked the UK government to move quickly to formalise its divorce from the EU but May has indicated that she will not be rushed into triggering the formal procedure for Brexit.

"We will have difficult negotiations with Britain, it will not be easy," Germany's Chancellor Angela Merkel said on Monday.

France has called for the rapid execution of the procedures for Britain to leave the EU, with government spokesman Stephane Le Foll telling reporters on Wednesday that Paris's position remained unchanged with the arrival of May as the UK's prime minister.